diff --git a/channels/h323/caps_h323.cxx b/channels/h323/caps_h323.cxx
index 573d24b90e..2cbb743dd4 100644
--- a/channels/h323/caps_h323.cxx
+++ b/channels/h323/caps_h323.cxx
@@ -1,5 +1,6 @@
 #include <ptlib.h>
 #include <h323.h>
+#include <h245.h>
 #include "caps_h323.h"
 
 #define DEFINE_G711_CAPABILITY(cls, code, capName) \